1. Field of the Invention
The present invention is directed to cutting blades for rotating wood working machines for planing or jointing wood or similar material surfaces and particularly to multi-edged cutting blades.
2. Prior Art
Straight knife tool geometry and knife maintenance has remained essentially unchanged since the advent of jointers and planers. The static state of knife maintenance, principally knife changing, re-setting and shifting, however, was recently significantly improved and perfected by certain revolutionary inventions of the present inventor. It is now possible to quickly, easily and accurately re-set, change or shift jointer or planer knives relative to their specific cutterhead or out-feed table positions in approximately one-tenth the time traditionally required. Which inventions are embodied in, respectively, a U.S. Pat. No. 4,854,051, entitled "Improved Jig for Aligning Cutter Blades", and U.S. patent application, Ser. No. 751,890, entitled "Jig for Aligning Cutter Blades to a Cutterhead". With the advent of these devices the disagreeable, frustrating and time consuming tasks of exactly aligning cutting blades to a machine table or cutterhead outside diameter have been greatly simplified. Additionally, the machine operator need no longer be intimidated by removing and replacing blades in a machine cutterhead.
Recognizing that blades or knifes can now be easily adjusted and replaced in planers, jointers and like woodworking machines, it was recognized by the present inventor that it would be appropriate to design blades that are suited for a particular application. Specifically, it is well known that a woodworking blade or knife optimum sharpness angle will be different for soft and hard woods or various contemporary composite materials such as plywoods and particle boards. Heretofore, the inherent difficulties involved in adjusting and changing cutterhead blades or knives for the wide range of materials which could be shaped or surfaced with such machines precluded the large scale manufacture of special purpose knives. Accordingly, the blades or knives manufactured for such machines have traditionally involved a cutting edge having a sharpness angle that was suitable, but not optimal, for working different types and varieties of wood or materials. Further, such blades or knives have generally involved a single ground edge only, rather than being ground along both edges as is the blade or knife of the present invention. The conventionally accepted "general purpose knife angle has evolved over the years to thirty-six (36) degrees, although angles ranging from as little as twenty-two (22) degrees to as much as forty-eight (48) degrees can be used for machining various woods or wood composite materials.
A recent patent to Grabovac, U.S. Pat. No. 4,658,875, however, does show a double edged blade for use with an improved knife holder. The Grabovac patent, however, does not teach a blade having opposite cutting edges with different sharpness angles as would be optimal for different needs and, of course, does not anticipate a blade having different sharpness angles formed in the same blade edge as does a blade or knife embodiment of the present invention. Neither does Grabovac offer a resharpening feature with his system, which is a valuable economic advantage in considering knife longevity. Rather, he teaches the disposal of dulled or nicked knives and their total replacement with new knives.
Within the woodworking blade or knife art, the present inventor is aware of only a single patent, U.S. Pat. No. 4,628,976, that is directed to a woodworking blade. This blade, however, unlike the present invention, has an edge as the blade end thereof that forms, essentially, a right angle to the blade body.